1. Field of the Invention
The present invention relates to a polymer-based protective film coating mixture and more particularly relates to a polyvinyl, polyalkyl acrylate or polyvinyl alcohol based film coating mixture that is strippable, re-wettable, heat-resistant and machinable.
2. Description of Related Art
Various types of film coating compositions are known in the art and have a wide range of applications. Most of these films are polymer based films. In some instances, the films are sprayed on and then allowed to dry to a coherent protective film such as the film disclosed in U.S. Pat. No. 5,143,949 to Grogan, et al., which is incorporated herein by reference.
Other films, such as the one disclosed in U.S. Pat. No. 4,632,847 to Lomasney, et al. are also known. The film in Lomasney, et al. is directed to a polymeric membrane for isolating hazardous materials within an area, such as an asbestos removal job site. The polymer is applied in liquid form to surfaces which are to be protected. Upon cure, a seamless bladder-like membrane is formed which isolates the work area and prevents the spread of airborne, or water-carried particulate matter by way of a "capturing" component that is present in the coating. The membrane can then be peeled from the surface and compacted for disposal.
While Lomasney, et al. works well for asbestos clean-up applications, it has deficiencies that prevents it from being applicable to other industrial applications such as in the automobile and aeronautical industries. For example, in both of these industries, it is highly desirable to have a protective film that can re-wet and be removed with water, if desired. The film in Lomasney, et al. is a tightly knit membrane that is resistant to water, which hinders it from having a practical use in applications that require a water-removable film coating.
Another film mixture known in the art is U.S. Pat. No. 4,064,092 to Burroway, et al. This film is directed to a mixture comprised of water reducible resin that is prepared from a balance of hydrophobic enhancing and hydrophilic enhancing monomers, solvents and plasticizers. The mixture yields a film that is substantially water insoluble. As such, this film also suffers from the same deficiencies as the film in Lomasney, et al, that is, it is substantially water insoluble. Thus, for the same reasons as given above for Lomasney, et al., it has limited application in any industry that requires a strong, water-removable protective film coating.
One industry that desires a water-removal protective film coating is the automobile industry. A need exists for a water-removable coating composition to protect the automobile against weathering, contamination from the atmosphere, chemical attack or accidental damage during manufacturing, handling, storage and transit. Typically, the vehicle's paint finish experiences significant in-house mutilation and physical damage on the assembly line. During assembly of the vehicle, the paint finish is inadvertently dinged, chipped and scratched as the workers use their tools to assemble the various parts of the vehicle. As a result, the vehicle's paint finish must undergo a costly and time consuming touch-up procedure to repair this inadvertent damage. Therefore, it is very advantageous to have the vehicle's paint finish protected by a film.
Presently, some automobile manufacturers are using such measures as plastic wrap, bubble paper, snap-on plastic body guard armor to protect the various parts of the automobile during the manufacturing process.
Each of these measures suffers from distinct disadvantages. For instance, while both the plastic wrap and bubble paper adequately protect the vehicle's paint finish during the manufacturing process and can be easily stripped off, they are highly labor intensive to put on the vehicle. The wrap and bubble paper are manufactured in large sheets that must be sized and cut to fit the various parts of the automobile to be protected. The sizing, cutting, and particularly, the application take a great deal of time and effort, which increases the manufacturing costs of each automobile.
In addition, if left on for to long a period, the bubble paper and the wrap can damage the paint. The bubble paper may damage the paint because it has an adhesive that can attack the paint if left on too long. The wrap, which is a polyethylene based film can damage the paint because the it does not "breath.", that is it does not allow gases to escape through the film. After a paint is applied to a vehicle and dried, the paint continues to cure for several weeks thereafter. This curing process produces volatile gases that emanate from the paint. If the gases become trapped between the finish and the film, chemical reactions can take place that can damage the paint finish. Moreover, the wrap and bubble paper are costly to purchase and dispose of.
The snap-on body armor also requires a substantial amount of time and effort to put on the vehicle and is also costly to purchase. Additionally, this armor is hard enough to scratch the paint, thus, being the source of the very problem that is was designed to solve.
Another disadvantage from which each of these three protective measures suffer is that they are usually removed as the vehicle leaves the assembly line. This, of course, leaves the paint finish completely unprotected during transit to the point-of-sale. During transit, the vehicle is exposed to further chemical and physical damage. Chemical damage can occur through acids from rain or animals that may come into contact with the paint finish. Physical damage can occur by gravel from the road projected against the paint finish by other vehicles and hot iron rail shavings produced during rail train transport. The hot iron shavings get on the surface of the paint finish and embeds in the clear coat. The metal shavings begin to oxidize, which causes freckles to appear in the paint finish. Thus, there is a need from a tough film that is inexpensive to apply and remove and one that can remain on the vehicle until the consumer purchases the car. There is also a need for a film that can be removed with water to lessen the time and expense of removal for the automobile dealerships.
The presently known water-removable films are applicable to the extent that they can be removed with water without being a danger to the environment. However, they re-wet too quickly, which is a disadvantage is some applications. One such application occurs in the assembly line.
While it is desirable that the protective film be a water-removable coating, it is equally desirable that the film be less re-wettable than presently known formulations because the vehicle must undergo a water-tight test during the assembly process in which the vehicle is moved to a "water bath" treatment area where it is heavily sprayed with water to test for leaks.
In some instances, the vehicle may be delayed in the "water bath" area, thereby exposing the film to substantial amounts of water. If the film absorbs too much water, it may become soft and tear or come off when the vehicle and film are subjected to high winds in a high velocity wind tunnel. In such applications, it is very important that the film not re-wet too quickly. It is equally important, however, that water infiltration into the film eventually occur because the film must be able to be re-wetted so that it can be removed with water after the vehicle reaches its final destination.
Thus, a need exists in the automobile industry for an environmentally safe polymer film that does not damage the paint when left on for extended periods of time, that can be easily applied and removed with water and that is tough enough to withstand the various physical and chemical stress to which the film is subjected during storage and transit.
Another needs exists for an environmentally safe, tough, machinable film that can be easily removed with water or physically peeled off the substrate. Such coatings have application, particularly in the aircraft industry where it is desirable to have coatings applied to large aluminum skins and components to protect them from damage during the manufacturing and subassembly stages.
The aircraft industry currently employs amine-based coatings that require the dried film to be removed with high volatile organic solvents, such as methylethyl ketone-based solvents. However, this film is riddle with various problems. For example, the removal process is expensive because of the cost associated with the use of the organic solvents used to remove the amine-based coating. Further, the conventional coatings do not fully protect the skins, thereby, requiring many hours of coating removal, polishing and re-surfacing or finishing work to bring the skins to manufacturers' specifications. These additional re-furbishing steps, of course, increases manufacturing costs.
Additionally, these conventional amine coatings have serious ramifications for the environment as well because of the large amounts of volatile organic compounds (VOCs) that are released into the atmosphere during their application and removal. For example, it takes approximately 300 gallons of amine-based remover to remove the amine-based coating from an average sized airliner and then about 250 gallons of methylethyl ketone per aircraft to remove the residue left by the amine-based remover. Additionally, the amine coating looses its ability to release, which requires larger volumes of stronger solvents.
In addition to the cost and environmental concerns, these conventional amine based coatings lack the flexibility and adhesion required to adequately protect the aluminum surface during the manufacturing process.
It is desirable to drill and machine the aluminum skin with the protective film still in tact on the aluminum surface so that the skin will be protected during the manufacturing process. Additionally, the shape of the aluminum skin sections are often formed by "drop hammer forging", which is a process that subjects the aluminum skin's surface to tremendous weight-pressure forces or process using hydraulic pressure. If the film does not have the required degree of flexibility and adhesion, it tears and begins to peel off when it is drilled through, which leaves the surface suspectable to scratches and other physical damage during the drop hammer forging or hydraulic pressure processes.
Other conventional films, such as the one covered by U.S. Pat. No. 5,143,949 are water-removable and bio-degradable, which solves the cost and environmental problems, but they lack the flexibility and adhesion required for the above-discussed machinable applications. Thus, there exists a need for a tough, machinable, strippable film that is environmentally safe and easy to apply and remove.
Another industrial application that has a need for a tough, strippable, heat-resistance film is the laminate countertop industry. Laminate countertops are well known in the art and have grown in popularity over the years. This increase in demand has caused manufacturers to move to mass production of various types of laminated countertops. A problem that has arisen concerns physical damage, such as chips and scratches that occur to the laminate top during the production process. Prior known formulations have encountered the problem of not being able to withstand the extreme temperatures (about 400.degree. F.) associated with molding the laminate to the countertop. When the temperatures reach this extreme level, conventional protective films begin to adhere to the laminate. Thus, the films must be removed prior to lamination to prevent the substantial amount of manufacturing time that would be devoted to tediously removing the adhered protective film coating. Thus, there is a need for a tough, strippable, heat-resistant protective film that can withstand the higher temperatures associated with some industrial applications.
Therefore, it can readily be seen that there is a need in the art for a tough, machinable, heat-resistant film that can be easily physically removed, removed with water or air pressure. The present invention provides a mixture that yields a film that addresses these needs.